Methods for preparing zeolites with surfactant-templated mesoporosity and tunable aluminum content

ABSTRACT

Compositions and methods for preparing mesoporous and/or mesostructured materials from low SAR zeolites are provided herewith. In particular, methods are provided that involve: (a) providing a low SAR zeolite, (b) optionally subjecting the low SAR zeolite to an acid framework modification, and (c) subjecting the framework-modified zeolite to a mesopore formation treatment. The resulting mesoporous zeolites can have bi-modal mesoporosity and higher aluminum contents relative to existing mesoporous zeolites.

RELATED APPLICATIONS

This application claims the priority benefit under 35 U.S.C. § 119(e) ofU.S. Provisional Patent Application Ser. No. 62/098,157 entitled“METHODS FOR PREPARING ZEOLITES WITH SURFACTANT-TEMPLATED MESOPOROSITYAND TUNABLE ALUMINUM CONTENT,” filed Dec. 30, 2014, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

One or more embodiments of the invention relate to compositions andmethods for preparing mesoporous zeolites from low Si/Al zeolites. Moreparticularly, embodiments described herein relate to the preparation ofmesoporous zeolites via a framework modification step followed by amesopore introduction step.

2. Description of the Related Art

Previously, methods have been described for introducing mesoporosityinto zeolites such as, for example, in U.S. Pat. No. 7,589,041. Thesezeolites, namely CBV 720 provided by Zeolyst International, have a highsilicon-to-aluminum ratio (“Si/Al”) and a low framework aluminumcontent. As previously described, this zeolite can be treated in thepresence of a pore forming agent (e.g., a surfactant) at a controlled pHunder a set of certain time and temperature conditions to introducemesoporosity into the zeolite. Thereafter, the mesostructured materialcan be treated to remove the pore forming agent (e.g., by calcination orchemical extraction). Although advances have been made in the art ofintroducing mesoporosity into zeolites, improvements are still needed.

SUMMARY

One or more embodiments of the present invention concern a method forforming a mesoporous zeolite. Generally, the method comprises: (a)modifying an initial zeolite to thereby yield a lower SAR zeolite,wherein the lower SAR zeolite has a silica to alumina molar ratio thatis at least 5 percent lower than the initial zeolite, but higher thanthe destabilizing SAR value of the initial zeolite; and (b) contactingat least a portion of the lower SAR zeolite with a pore forming agent tothereby form the mesoporous zeolite.

One or more embodiments of the present invention concern a method forforming a mesoporous zeolite. Generally, the method comprises: (a)providing a low SAR zeolite, wherein the low SAR zeolite is selectedfrom the group consisting of a ZSM-5 having a silica to alumina molarratio of 17 or less, a mordenite having a silica to alumina molar ratioof 10 or less, a faujasite having a silica to alumina molar ratio of 5or less, a BEA zeolite having a silica to alumina molar ratio of 15 orless, a LTL zeolite having a silica to alumina molar ratio of 5 or less,an FRE zeolite having a silica to alumina molar ratio of 10 or less, andmixtures thereof; and (b) contacting at least a portion of the low SARzeolite with a pore forming agent to thereby form the mesoporouszeolite.

One or more embodiments of the present invention concern a method forforming a mesoporous zeolite. Generally, the method comprises: (a)subjecting an initial zeolite to a framework modification process tothereby produce a framework-modified zeolite, wherein theframework-modified zeolite has a silica to alumina molar ratio that islower than the initial zeolite; (b) contacting at least a portion of theframework-modified zeolite with an acid to thereby form an acid-treatedzeolite; and (c) contacting at least a portion of the acid-treatedzeolite with a pore forming agent to thereby form the mesoporouszeolite.

One or more embodiments of the present invention concern a low SARzeolite, wherein the low SAR zeolite is selected from the groupconsisting of a ZSM-5 having a silica to alumina molar ratio of 17 orless, a mordenite having a silica to alumina molar ratio of 10 or less,a faujasite having a silica to alumina molar ratio of 5 or less, a BEAzeolite having a silica to alumina molar ratio of 15 or less, a LTLzeolite having a silica to alumina molar ratio of 5 or less, an FREzeolite having a silica to alumina molar ratio of 10 or less, andmixtures thereof.

One or more embodiments of the present invention concern a mesoporouszeolite, wherein the mesoporous zeolite has a dV/log(d) in the range of0.3 to 100 and a mesopore ratio in the range of 0.2 to 1.2.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention are described herein with referenceto the following drawing figures, wherein:

FIG. 1 depicts the Ar sorption isotherms of the treated zeolites inExample 4;

FIG. 2 depicts NLDFT (non-local density function theory) pore sizedistributions of the treated zeolites in Example 4;

FIG. 3 depicts the Ar sorption isotherms of the treated zeolites inExample 6;

FIG. 4 depicts NLDFT pore size distributions of the treated zeolites inExample 6;

FIG. 5 depicts the Ar sorption isotherms of the treated zeolite inExample 7;

FIG. 6 depicts NLDFT pore size distributions of the treated zeolite inExample 7;

FIG. 7 depicts the Ar sorption isotherms of the treated zeolites inExample 9;

FIG. 8 depicts NLDFT pore size distributions of the treated zeolites inExample 9;

FIG. 9 depicts powder X-ray diffraction patterns of the samples inExample 10;

FIG. 10 depicts the Ar sorption isotherms of the treated zeolites inExample 11; and

FIG. 11 depicts the Ar sorption isotherms of the treated zeolites inExample 12.

DETAILED DESCRIPTION

Generally, the process described herein enables the introduction ofbi-modal mesoporosity into zeolites that were previously resistant tosuch treatments. In particular, in various embodiments, the processinvolves providing a zeolite having a low silica to alumina molar ratio(also referred to herein as “SAR”) and subjecting this low SAR zeoliteto further treatments to produce a mesoporous zeolite.

One advantage of the process described herein is that it can producemesoporous zeolites with higher aluminum contents than were previouslyavailable and, in some cases, with higher aluminum contents than areachievable in the synthesis process. An additional benefit of theprocess described herein is that it can introduce bi-modal mesoporosityinto the zeolite. As used herein, “bi-modal mesoporosity” refers to theintroduction of desilicated large mesopores and surfactant-templatedsmall mesopores into the zeolite.

In various embodiments, the low SAR zeolites used herein can be producedby directly synthesizing or crystallizing the low SAR zeolite,desilicating an initial zeolite, or aluminating an initial zeolite.

As used herein, a “low SAR zeolite” refers to a zeolite that has asilica to alumina molar ratio that is lower compared to conventionalzeolites of the same species. For example, these low SAR zeolites caninclude, but are not limited to, ZSM-5, mordenite, faujasite, BEAzeolite, LTL zeolite, and/or FRE zeolite containing silica to aluminamolar ratios that are lower when compared to commercially-availablezeolites of the same species. It should be noted that the 3-letter namesof the zeolites follow the IZA (International Zeolite Association)nomenclature.

In various embodiments, the low SAR zeolite can be a ZSM-5 having asilica to alumina molar ratio of at least 2, 3, or 4 and/or not morethan 20, 19, 18, 17, 16, 15, 14, 13.5, or 13. Furthermore, in certainembodiments, the low SAR zeolite can be a ZSM-5 having a silica toalumina molar ratio in the range of 2 to 17, 2 to 16, 3 to 15, 3 to 14,4 to 13.5, or 4 to 13. The silica to alumina molar ratios of thezeolites can be calculated from XRF analyses.

In various embodiments, the low SAR zeolite can be a mordenite having asilica to alumina molar ratio of at least 2, 3, or 4 and/or not morethan 12, 11, 10, 9.5, 9, 8.5, or 8. Furthermore, in certain embodiments,the low SAR zeolite can be a mordenite having a silica to alumina molarratio in the range of 2 to 10, 2 to 9.5, 3 to 9, 3 to 8.5, or 4 to 8.

In various embodiments, the low SAR zeolite can be a faujasite having asilica to alumina molar ratio of 2, 2.5, or 3 and/or not more than 5,4.5, 4, or 3.5. Furthermore, in certain embodiments, the low SAR zeolitecan be a faujasite having a silica to alumina molar ratio in the rangeof 2 to 5, 2 to 4.5, 2.5 to 4, or 3 to 4. In certain embodiments, thefaujasite can comprise zeolite Y.

In various embodiments, the low SAR zeolite can be a BEA zeolite havinga silica to alumina molar ratio of at least 2, 3, or 4 and/or not morethan 15, 14, 13, or 12. Furthermore, in certain embodiments, the low SARzeolite can be a BEA zeolite having a silica to alumina molar ratio inrange of 2 to 15, 2 to 14, 3 to 13, or 4 to 12.

In various embodiments, the low SAR zeolite can be an LTL zeolite havinga silica to alumina molar ratio of 2, 2.5, or 3 and/or not more than 5,4.5, 4, or 3.5. Furthermore, in certain embodiments, the low SAR zeolitecan be an LTL zeolite having a silica to alumina molar ratio in therange of 2 to 5, 2 to 4.5, 2.5 to 4, or 3 to 4.

In various embodiments, the low SAR zeolite can be an FRE zeolite havinga silica to alumina molar ratio of at least 2, 3, or 4 and/or not morethan 10, 9.5, 9, 8.5, or 8. Furthermore, in certain embodiments, the lowSAR zeolite can be an FRE zeolite having a silica to alumina molar ratioin the range of 2 to 10, 2 to 9.5, 3 to 9, 3 to 8.5, or 4 to 8.

In one or more embodiments, the present invention is directed to aprocess that combines an initial treatment that increases the aluminumcontent of an initial zeolite (e.g., by desilication or alumination) andone or more subsequent treatment steps to impart mesoporosity in thealuminum-enriched zeolite. In various embodiments, this initialtreatment can involve modifying an initial zeolite to thereby producethe low SAR zeolite. This modifying step can include a frameworkmodification process such as, for example, a desilication step and/or analumination step. One advantage of the modifying step described hereinis that it can allow independent control of the aluminum content of thesubsequently produced mesoporous zeolites.

The initial zeolite subjected to the modifying step can comprise aZSM-5, a mordenite, a faujasite, a BEA zeolite, a LTL zeolite, an FREzeolite, or combinations thereof. As used herein, “zeolite” can compriseany one of the zeolitic materials listed in the database of zeolitestructures by the International Zeolite Association (IZA). In variousembodiments, the initial zeolite can have a silica to alumina molarratio that is less than 100, 75, 50, 40, 30, 20, 15, or 10 and more than3, 4, 5, 6, or 7.

In one or more embodiments, the initial zeolite starting materials canhave a total 20 to 80 Å diameter mesopore volume of less than 0.01 cc/g.Additionally, suitable initial zeolites can have a total 1 to 20 Åmicropore volume of at least 0.3 cc/g. Furthermore, the initial zeolitecan have an average unit cell size (“UCS”) of at least 24.40, at least24.45, or at least 24.50 Å. In certain embodiments, the initial zeolitehas not been previously subjected to any forms of pretreatmentincluding, for example, steam treatment, thermal treatment,dealumination, and/or desilication. Additionally, in variousembodiments, the initial zeolite can be present as a component of acomposite material. Such composite materials can further include, forexample, one or more binder material components.

In various embodiments, the modifying step can comprise an aluminationtreatment. Generally, this alumination treatment can involve treatingthe initial zeolite with an aluminum source under proper conditions inorder to produce the low SAR zeolite. In certain embodiments, thisaluminum source can comprise sodium aluminate.

In various embodiments, the modifying step can comprise a desilicationtreatment. The conditions of the desilication process may vary dependingon the type of zeolite subjected to treatment. In certain embodiments,this desilication step can involve treating the zeolite in a basicsolution at an elevated temperature for an extended period of time.Generally, this basic desilication step can result in frameworkdesilication.

The length of the desilication step, including the base treatment, canvary depending on the type of zeolite species used. For example, thedesilication step can occur over a time period of 0.1 to 48 hours, 1 to24 hours, or 4 to 16 hours. Similarly, the temperature of thedesilication step can also vary depending on the type of zeolite treatedduring the process. For example, the desilication step, including thebase treatment, can occur at a temperature in the range of 20 to 160°C., 40 to 140° C., or 60 to 120° C.

Likewise, the pH of the desilication step can vary depending on the typeof zeolite treated in the process. For example, the base in thedesilication treatment can have a pH of at least 8, in the range of fromabout 8 to about 14, in the range of from about 8 to about 12, or in therange of from about 9 to about 11. Any base suitable for providing a pHin the desired range may be employed. In various embodiments, the basecan be selected from the group consisting of ammonium hydroxide,tetraalkyl ammonium hydroxides, sodium hydroxide, potassium hydroxide,sodium carbonate, potassium carbonate, amines, and mixtures of two ormore thereof. In certain embodiments, the base comprises sodiumhydroxide.

Consequently, the pH, temperature, and time parameters can be importantfor achieving the target silica to alumina molar ratio in thedesilicated zeolite. For example, initial zeolites with higher silica toalumina molar ratios may require milder desilication conditions (e.g.,milder pH, lower temperatures, and shorter time) compared to initialzeolites with lower silica to alumina molar ratios. Thus, varying thedesilication conditions can allow greater access into the initialzeolites with lower silica to alumina molar ratios, which may not beaccessible by direct synthesis.

Though not wishing to be bound by theory, it is believed that contactingthe above-described initial zeolite with a base may cause at leastpartial desilication of the initial zeolite. Accordingly, in variousembodiments, contacting the initial zeolite with a base may produce anat least partially desilicated zeolite. Furthermore, in certainembodiments, some desilication-based mesoporosity may be introduced intothe zeolite during the desilication step.

In certain embodiments, the base treatment can increase the average unitcell size (“UCS”) of the initial zeolite. For example, the low SARzeolite can have a UCS that is at least 0.01, at least 0.02, at least0.03, at least 0.04, at least 0.05, or at least 0.06 Å greater than theUCS of the initial zeolite.

In various embodiments, the desilication treatment decreases the zeolitesurface area (“ZSA”) and the Brunauer-Emmett-Teller (“BET”) surface areaof the initial zeolite, while increasing the matrix surface area (“MSA”)of the initial zeolite. The BET surface area can be formulated bycombining the ZSA and MSA of the zeolite. All surface areas are measuredby applying BET theory and observing t-plot analysis of the gas sorptionresults.

For example, the low SAR zeolite can have a ZSA that is at least 10, 20,30, 40, or 50 percent and/or not more than 200, 150, 125, 100, or 95percent lower than the ZSA of the initial zeolite. In other embodiments,the low SAR zeolite can have a BET that is at least 10, 20, 30, 40, or50 percent and/or not more than 200, 150, 125, 100, or 95 percent lowerthan the BET of the initial zeolite. Furthermore, in certainembodiments, the low SAR zeolite can have a MSA that is at least 10, 30,50, 100, or 200 percent and/or not more than 1,000, 750, 500, 400, or300 percent greater than the MSA of the initial zeolite.

In various embodiments, the aforementioned modifying step can yield alow SAR zeolite having a silica to alumina molar ratio that is lowerthan the silica to alumina molar ratio of the initial zeolite, but thatis still higher than the destabilizing SAR value of the initial zeolite.As used herein, the “destabilizing SAR value” defines the SAR value atwhich the relative crystallinity of the modified zeolite drops to below10 percent of the crystallinity of the initial zeolite as measured byX-ray diffraction (“XRD”) or the SAR value below which anothercrystalline phase appears. In certain embodiments, the low SAR zeolitecan have a silica to alumina molar ratio at which the relativecrystallinity of the modified zeolite drops to below 15, 20, or 25percent of the crystallinity of the initial zeolite as measured by XRD.As would be understood by one of ordinary skill in the art, thecrystalline content of a zeolite can be measured by XRD and is typicallyexpressed relative to the initial zeolite or another zeolite of the samestructure as crystallinity standard. Thus, in various embodiments, thedifference in crystalline content between the initial zeolite and thelow SAR zeolite can be determined by XRD. Methods for determining thecrystalline content of a zeolite are generally known to those ofordinary skill in the art.

Subsequent to the modifying step, the resulting low SAR zeolite can havea lower silica to alumina molar ratio compared to the initial zeolite.For example, the low SAR zeolite can have a silica to alumina molarratio that is at least 5, 10, 15, 20, 25, 30, 35, or 40 and/or not morethan 80, 75, 70, 65, or 60 percent lower than the initial zeolite.Furthermore, in certain embodiments, the low SAR zeolite can have asilica to alumina molar ratio that is lower than 25, 20, 18, 17, 16, 15,14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4.

Additionally or alternatively, the resulting low SAR zeolite can have ahigher aluminum content compared to the initial zeolite. For example,the aluminum content of the low SAR zeolite can be at least 5, 10, 15,20, 25, 30, 40, 50, 60, or 75 percent greater than the aluminum contentof the initial zeolite.

In various embodiments, the low SAR zeolite can have a crystallinecontent that is less than the crystalline content of the initial zeoliteas measured by XRD. In one or more embodiments, the modifying step canbe sufficient to reduce the crystalline content of the initial zeoliteby at least 1, 5, 10, 15, 20, 25, 30, 35, or 40 percent.

Accordingly, in one or more embodiments, the low SAR zeolite can have acrystalline content that is less than the crystalline content of theinitial zeolite, such as, for example, at least 1, 5, 10, 15, 20, 25 30,35, or 40 percent less than the crystalline content of the initialzeolite as measured by XRD. In further embodiments, the low SAR zeolitecan have a reduced crystalline content that is within 50, 45, 40, 35,30, 25, 20, 15, or 10 percent of the initial zeolite.

In various embodiments, the low SAR zeolite can have more mesopores thanthe initial zeolite. For example, the low SAR zeolite can have a total20 to 80 Å diameter mesopore volume that is at least 5, 10, 20, 30, 40,50, 60, 70, 80, 90, 100, 200, 300, 400, or 500 percent greater than the20 to 80 Å diameter mesopore volume of the initial zeolite. Furthermore,the low SAR zeolite can have a total 20 to 80 Å diameter mesopore volumethat is at least 0.002, 0.004, 0.005, 0.008, 0.01, 0.02, or 0.05 cc/ggreater than the total 20 to 80 Å diameter mesopore volume of theinitial zeolite.

In one or more embodiments, the low SAR zeolite can have a total 20 to80 Å diameter mesopore volume of at least 0.01, 0.02, 0.03, 0.04, or0.05 and/or not more than 0.3, 0.2, 0.15, 0.125, or 0.1 cc/g.Furthermore, in certain embodiments, the low SAR zeolite can have atotal 20 to 80 Å diameter mesopore volume in the range of 0.01 to 0.3,0.02 to 0.2, 0.03 to 0.15, 0.04 to 0.125, or 0.05 to 0.1 cc/g.

In one or more embodiments, the low SAR zeolite can have a total 20 to300 Å diameter mesopore volume that is at least 5, 10, 20, 30, 40, 50,60, 70, 80, 90, 100, 200, 300, 400, or 500 percent greater than the 20to 300 Å diameter mesopore volume of the initial zeolite. Furthermore,the low SAR zeolite can have a total 20 to 300 Å diameter mesoporevolume that is at least 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.1cc/g greater than the total 20 to 300 Å diameter mesopore volume of theinitial zeolite.

In one or more embodiments, the low SAR zeolite can have a total 20 to300 Å diameter mesopore volume of at least 0.05, 0.06, 0.07, 0.08, 0.09,0.10, 0.11, 0.12, 0.13, 0.14, or 0.15 cc/g. Additionally, the mesoporouszeolite can have a total 20 to 300 Å diameter mesopore volume in therange of from about 0.05 to about 0.70, in the range of from about 0.10to about 0.60 cc/g, or in the range of from about 0.15 to about 0.50cc/g.

In various embodiments, the low SAR zeolite can have a lower mesoporeratio than the initial zeolite. Based on one theory, the desilicationprocess (if utilized as the modifying step) can introduce some amount oflarger mesopores into the initial zeolite, thereby decreasing itsmesopore ratio. As used herein, the “mesopore ratio” is defined as thepore volume of pores having a 20 to 80 Å diameter (as determined byNLDFT analysis) divided by the pore volume of pores having a 20 to 300 Ådiameter (as determined by NLDFT analysis). For example, the low SARzeolites can have a mesopore ratio that is at least 5, 10, 15, 20, 40,or 50 percent lower than the mesopore ratio of the initial zeolite.Additionally or alternatively, the low SAR zeolite can have a mesoporeratio that is at least 0.05, 0.1, 0.15, 0.2, or 0.25 lower than themesopore ratio of the initial zeolite.

In alternative embodiments, the low SAR zeolite can have a greatermesopore ratio relative to the initial zeolite.

In one or more embodiments, the initial zeolite can have a mesoporeratio of at least 0.1, 0.2, 0.3, or 0.4 and/or not more than 0.9, 0.8,0.7, or 0.6. Furthermore, in certain embodiments, the initial zeolitecan have a mesopore ratio in the range of 0.1 to 0.9, 0.2 to 0.8, 0.3 to0.7, or 0.4 to 0.6. In other embodiments, the low SAR zeolite can have amesopore ratio of at least 0.1, 0.2, 0.1, 0.2, 0.3, or 0.4 and/or notmore than 0.9, 0.8, 0.7, or 0.6. Moreover, in certain embodiments, thelow SAR zeolite can have a mesopore ratio in the range of 0.1 to 0.9,0.2 to 0.8, 0.3 to 0.7, or 0.4 to 0.6.

In various embodiments, the low SAR zeolite has a higher nPA-TPDrelative to the initial zeolite. The “nPA-TPD” refers to then-propylamine temperature programmed desorption. As would be appreciatedby one skilled in the art, the nPA-TPD can indicate the Brønsted acidityof the zeolite sample. For example, the low SAR zeolite can have annPA-TPD that is at least 5, 10, 15, or 20 percent and/or not more than200, 100, 90, or 75 percent greater than the initial zeolite.Furthermore, in certain embodiments, the low SAR zeolite can have anPA-TPD that is at least 5 to 200 percent, 10 to 100 percent, 15 to 90percent, or 20 to 75 percent greater than the initial zeolite.

Subsequent to the modifying step, the resulting low SAR zeolite can befiltered, washed, and dried to yield a dried low SAR zeolite or can besubjected to other treatment after filtration and washing withoutdrying. In one or more embodiments, following the modifying step, thelow SAR zeolite can be vacuum filtered and washed with water. After thewater wash, the low SAR zeolite can be filtered again. Any filtering andwashing techniques known or hereafter discovered in the art may beemployed for these steps.

In one or more embodiments, the optional drying step can include dryingat a temperature in the range of from about 20 to about 150° C., in therange of from about 50 to about 120° C., or in the range of from 70 to90° C. Furthermore, the drying step can be performed for a time periodof at least 5 minutes, at least 30 minutes, or at least 1 hour. In otherembodiments, the drying step can be performed for a time period in therange of from about 5 minutes to about 24 hours, in the range of fromabout 15 minutes to about 12 hours, or in the range of from 30 minutesto 2 hours.

In various embodiments, prior to introducing additional mesoporosityinto the low SAR zeolite, the low SAR zeolite can be subjected to anacid treatment to thereby yield an acid-treated zeolite. In certainembodiments, the acid treatment can increase the silica to alumina molarratio of the low SAR zeolite by removing aluminum therefrom. Forexample, the acid-treated zeolite can have a silica to alumina molarratio that is at least 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 percenthigher than the low SAR zeolite. Additionally or alternatively, theacid-treated zeolite can have a silica to alumina molar ratio that isnot more than 300, 200, 150, 100, or 65 percent higher than the low SARzeolite.

Generally, the acid treatment can involve contacting at least a portionof the low SAR zeolite with an acid. In one or more embodiments, the lowSAR zeolite can be modified by exposing the low SAR zeolite in asolution containing an acid for a certain amount of time andtemperature. The acid chosen can be any acid sufficient to produce anacid solution having a pH of less than 6, less than 4, less than 3, inthe range of from about 1 to about 6, in the range of from about 2 toabout 4, or in the range of from about 4 to about 6. The acid employedduring the acid framework modification can be any known or hereafterdiscovered mineral acid, organic acid, or mixtures of two or morethereof. Furthermore, in various embodiments, the acid employed can alsobe a chelating agent.

Additionally, one or more complexing agents can be employed during theacid framework modification. In various embodiments, the acid selectedfor use herein can be a dealuminating acid. Specific examples of acidssuitable for use in the various embodiments described herein include,but are not limited to, hydrochloric acid, sulfuric acid, nitric acid,acetic acid, sulfonic acid, oxalic acid, citric acid,ethylenediaminetetraacetic acid (“EDTA”), tartaric acid, malic acid,glutaric acid, succinic acid, and mixtures of two or more thereof. Incertain embodiments, the acid is not hydrofluoric acid.

In one or more embodiments, a buffer solution can be employed during theacid framework modification that uses a weak acid in combination with aweak acid salt to give a constant pH. For example, in one embodiment,citric acid can be used with ammonium citrate to produce a constant pH,while other weak acids and weak acid salts can also be used.

During the acid framework modification, the acid can be present in anamount in the range of from about 1 to about 10, or in the range of from1.5 to 4 milliequivalents per gram of lower SAR zeolite (“meq/g”). Infurther embodiments of the acid framework modification, the acid can bepresent in an amount of at least about 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, or4.5 and/or not more than 10, 9, 8.5, 8, 7.5, 7, 6.5, or 6 meq/g.

In certain embodiments, the concentration of the acid used for the acidframework modification can influence the subsequent mesopore volumes andsizes in the acid-modified zeolites. In such embodiments, the increaseof acid severity used in the acid framework modification can becorrelated with the increasing mesopore volumes andpore-size-distribution (“POSD”). Furthermore, the acid frameworkmodification can be performed at a temperature in the range of fromabout 20 to about 200° C., or in the range of from room temperature toabout 100° C. Moreover, the acid framework modification can be performedover a time period ranging from about 1 minute to about 12 hours, in therange of from about 1 minute to about 4 hours, or in the range of from30 minutes to 2 hours. In one or more embodiments, the initial zeoliteis not steamed prior to acid framework modification.

In one or more embodiments, following the acid framework modification,the framework-modified zeolite can be vacuum filtered and washed withwater. Any filtering and washing techniques known or hereafterdiscovered in the art may be employed for these steps.

In one or more embodiments, the optional drying step can include dryingat a temperature of at least 20° C., at least 50° C., or at least 80° C.Additionally, the drying step can be performed at a temperature in therange of from about 20 to about 150° C., in the range of from about 50to about 120° C., or in the range of from 70 to 90° C. Furthermore thedrying step can be performed for a time period of at least 5 minutes, atleast 30 minutes, or at least 1 hour. In other embodiments, the dryingstep can be performed for a time period in the range of from about 5minutes to about 24 hours, in the range of from about 15 minutes toabout 12 hours, or in the range of from 30 minutes to 2 hours.

In still other embodiments, the drying step can be omitted entirely. Inother words, after filtering the acid-treated framework-modifiedzeolite, the resulting wet cake can be directly subjected to thebelow-described mesopore formation process.

In various embodiments, the acid-treated zeolite can have a crystallinecontent that is less than the crystalline content of the low SAR zeoliteas measured by XRD. In one or more embodiments, the acid treatmentprocess can be sufficient to reduce the crystalline content of the lowSAR zeolite by at least 1, 2, 3, 4, 5, or 10 percent as measured by XRD.In further embodiments, the acid-treated zeolite can have a reducedcrystalline content that is within 50, 45, 40, 35, 30, 25, 20, 15, or 10percent of the initial zeolite.

In certain embodiments, the acid treatment process can decrease theaverage UCS of the low SAR zeolite. For example, the acid-treatedzeolite can have a UCS that is at least 0.01, 0.02, 0.03, 0.04, 0.05, or0.06 lower than the UCS of the low SAR zeolite.

In various embodiments, the acid treatment increases the zeolite surfacearea (“ZSA”), the matrix surface area (“MSA”), and theBrunauer-Emmett-Teller (“BET”) surface area of the low SAR zeolite. Forexample, the low SAR zeolite can have a ZSA, MSA, and/or BET that is atleast 10, 25, 50, 100, or 150 percent and/or not more than 500, 400,300, 250, or 200 percent lower than the ZSA, MSA, and/or BET of theacid-treated zeolite. Furthermore, in certain embodiments, the low SARzeolite can have a ZSA, MSA, and/or BET that is 10 to 500 percent, 25 to400 percent, 50 to 300 percent, 100 to 250 percent, or 150 to 200percent lower than the ZSA, MSA, and/or BET of the acid-treated zeolite.

As mentioned above, the framework-modified zeolite (e.g., low SARzeolite or acid-treated zeolite) can be subjected to a mesoporeformation process in order to form at least one mesopore in theframework-modified zeolite. Methods for mesopore incorporationcontemplated by various embodiments of the present invention (e.g.,introduction of mesoporosity in zeolites) can generally include thefollowing steps:

-   -   1. Contacting the framework-modified zeolite with a pH        controlling medium, optionally in the presence of a pore forming        agent, under various time and temperature conditions.    -   2. Filtering, washing, and drying the zeolite.    -   3. Removing and/or recovering the pore forming agent (if        present), for example, by calcination (removal) and/or chemical        extraction (recovery).    -   4. The resulting material can also be chemically modified (e.g.,        by ion exchange with rare earths); blended with binders, matrix,        and additives; and shaped (e.g., into beads, pellets, and FCC        micropsheres).

In one or more embodiments, the mesopore formation process can beperformed employing any reagents and under any conditions described inU.S. Pat. No. 7,589,041, the entire disclosure of which is incorporatedherein by reference. For example, the temperature employed duringmesopore formation can range from about room temperature to about 200°C. The time period employed can be in the range of from about 2 hours(or less) to about 2 weeks.

In one or more embodiments, the mesopore formation process at leastcomprises contacting the above-described framework-modified zeolite witha base. In various embodiments, the above-mentioned pH controllingmedium can have a pH of at least 7, in the range of from about 8 toabout 14, in the range of from about 8 to about 12, or in the range offrom about 9 to about 11. Any base suitable for providing a pH in thedesired range may be employed. In various embodiments, the base can beselected from the group consisting of ammonium hydroxide, tetraalkylammonium hydroxides, sodium hydroxide, potassium hydroxide, sodiumcarbonate, potassium carbonate, amines, and mixtures of two or morethereof. In certain embodiments, the base comprises a mixture ofammonium hydroxide and sodium hydroxide.

As noted above, a pore forming agent may optionally be employed alongwith the pH controlling medium. In one or more embodiments, the poreforming agent can include a surfactant. When basic conditions areemployed, typically a cationic surfactant can be used. In one or moreembodiments, the surfactant employed can comprise one or morealkyltrimethylammonium salts and/or one or more dialkyldimethylammoniumsalts. In various embodiments, the surfactant can be selected from thegroup consisting of cetyltrimethyl ammonium bromide (“CTAB”),cetyltrimethyl ammonium chloride (“CTAC”), behenyltrimethylammoniumchloride (“BTAC”), and mixtures thereof. Other suitable pore formingagents include, but are not limited to, non-ionic surfactants, polymers(e.g., block copolymers), and soft templates.

In alternate embodiments, the mesopore introduction process can beperformed in the absence or substantial absence of a pore forming agent.Thus, in various embodiments, the mesopore introduction process can beperformed in the absence or substantial absence of a surfactant.Similarly, the mesopore introduction process can be performed in theabsence or substantial absence of any cationic surfactants, non-ionicsurfactants, polymers (e.g., block copolymers), and soft templates.

In various embodiments, following contact with the pH controlled medium,the zeolite can be subjected to thermal treatment. In variousembodiments, such thermal treatment can include contacting at least aportion of the zeolite with steam. In one or more embodiments, thezeolite can be contacted with steam having a temperature of at least450° C., at least 550° C., at least 650° C., or at least 700° C.Additionally, following contact with the pH controlled medium, thezeolite can be contacted with steam having a temperature in the range offrom about 450 to about 1,000° C., in the range of from about 500 toabout 950° C., in the range of from about 650 to about 950° C., in therange of from about 700 to about 850° C., or about 788° C. Thermaltreatment can be performed for a time period ranging from about 1 minuteto about 24 hours, about 5 minutes to about 12 hours, or about 10minutes to about 8 hours.

Following the pH controlled medium contacting step, the zeolite can befiltered, washed, and/or dried. In one or more embodiments, the zeolitecan be filtered via vacuum filtration and washed with water. Thereafter,the recovered zeolite can optionally be filtered again and optionallydried.

Following the filter, wash, and drying steps, the zeolite can besubjected to additional heat treatment or chemical extraction in orderto remove or recover at least a portion of the pore forming agent, ifemployed. In one or more embodiments, the zeolite can be calcined innitrogen at a temperature in the range of from about 500 to about 600°C., and then in air for pore forming agent (e.g., surfactant) removal.The pore forming agent removal technique is selected based, for example,on the time needed to remove all of the pore forming agent from thezeolite. The total time period employed for heat treatment of thezeolite can be in the range of from about 30 minutes to about 24 hours,or in the range of from 1 to 12 hours. In various embodiments, this caninclude subjecting the mesoporous zeolite to ammonium exchange,azeotropic distillation, calcination, or a combination thereof.

In various embodiments, the resulting mesoporous zeolite can besubjected to one or more post-formation treatments. Suitablepost-formation treatments are described, for example, in U.S. Pat. No.7,589,041, which, as noted above, is incorporated herein by reference inits entirety. In various embodiments, the mesoporous zeolite can besubjected to one or more post-formation treatments selected from thegroup consisting of calcination, ion exchange, steaming, incorporationinto an adsorbent, incorporation into a catalyst, silicon incorporation,incorporation into a membrane, and combinations of two or more thereof.Suitable ion exchange procedures for the resulting mesoporous zeoliteinclude, but are not limited to, ammonium ion exchange, rare earth ionexchange, lithium ion exchange, potassium ion exchange, calcium ionexchange, and combinations of two or more thereof.

In various embodiments, the resulting mesoporous zeolite can be amesostructured zeolite.

Accordingly, in various embodiments, the mesoporous zeolite can have asilica to alumina molar ratio that is at least 5, 10, 15, 20, 25, 30,35, 40, 45, or 50 percent higher than the low SAR zeolite. Additionallyor alternatively, the mesoporous zeolite can have a silica to aluminamolar ratio that is not more than 300, 200, 150, 100, 65, or 50 percenthigher than the low SAR zeolite.

Furthermore, in various embodiments, the resulting mesoporous zeolitecan have a crystalline content that is at least 1, 5, 10, 15, 20, 25,30, 35, or 40 percent greater than the framework-modified zeolite (e.g.,the low SAR zeolite or acid-treated zeolite). Furthermore, the resultingmesoporous zeolite can have a crystalline content that is at least 60,65, 70, 75, 80, 85, 90, 95, or 99 percent of the crystalline content ofthe above-described initial zeolite, as measured by XRD. In furtherembodiments, the mesoporous zeolite can have a crystalline content of atleast 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or99 weight percent, as measured by XRD.

In various embodiments, the resulting mesoporous zeolite can have atotal 20 to 80 Å diameter mesopore volume that is at least 5, 10, 20,30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, or 500 percent greaterthan the 20 to 80 Å diameter mesopore volume of the above-describedinitial zeolite, low SAR zeolite, or acid-treated zeolite. Furthermore,the mesoporous zeolite can have a total 20 to 80 Å diameter mesoporevolume that is at least 0.02, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1,or 0.2 cc/g greater than the total 20 to 80 Å diameter mesopore volumeof the initial zeolite, low SAR zeolite, or acid-treated zeolite.

In various embodiments, the mesoporous zeolite can have a total 20 to 80Å diameter mesopore volume of at least 0.05, 0.06, 0.07, 0.08, 0.09,0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.20, or 0.25 cc/g. Additionally,the mesoporous zeolite can have a total 20 to 80 Å diameter mesoporevolume in the range of from about 0.05 to about 0.70, in the range offrom about 0.10 to about 0.60 cc/g, or in the range of from about 0.15to about 0.50 cc/g.

In various embodiments, the resulting mesoporous zeolite can have atotal 20 to 300 Å diameter mesopore volume that is at least 5, 10, 20,30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, or 500 percent greaterthan the 20 to 300 Å diameter mesopore volume of the above-describedinitial zeolite, low SAR zeolite, or acid-treated zeolite. Furthermore,the mesoporous zeolite can have a total 20 to 300 Å diameter mesoporevolume that is at least 0.02, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1,or at least 0.2 cc/g greater than the total 20 to 300 Å diametermesopore volume of the initial zeolite, low SAR zeolite, or acid-treatedzeolite.

In various embodiments, the mesoporous zeolite can have a total 20 to300 Å diameter mesopore volume of at least 0.05, 0.06, 0.07, 0.08, 0.09,0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.20, or 0.25 cc/g. Additionally,the mesoporous zeolite can have a total 20 to 300 Å diameter mesoporevolume in the range of from about 0.05 to about 0.70, in the range offrom about 0.10 to about 0.60 cc/g, or in the range of from about 0.15to about 0.50 cc/g.

Due to the desilication treatment discussed above, at least two types ofmesopores can be introduced into the mesoporous zeolite: (1) desilicatedmesopores that have broad pore size distribution and (2) rived mesoporeswith much narrower pore size distribution. This phenomena can bedemonstrated by the NLDFT differential mesopore size distribution, whichcan be shown by the dV/log(D) values and/or the dV/D value of thezeolite. As used herein, “dV” is the first derivative of pore volume and“D” is the pore diameter in angstrom. For example, the mesoporouszeolite can have a dV/log(D) of at least 0.3, 0.35, 0.4, 0.45, 0.75, 1,1.5, 2, or 2.5 and/or not more than 100, 10, 9.5, 9, 8.5, 8, 7.5, 7, or6.5. Moreover, in certain embodiments, the mesoporous zeolite can have adV/log(D) value in the range of 0.3 to 10, 0.35 to 9.5, 0.4 to 9, 0.45to 8.5, 0.75 to 8, 1 to 7.5, 1.5 to 7, 2 to 6.5, or 2.5 to 6.5.Similarly, in various embodiments, the mesoporous zeolite can have adV/D of at least 0.002, 0.0035, 0.004, 0.0045, 0.0075, 0.01, 0.015,0.02, or 0.025 and/or not more than 0.1, 0.095, 0.09, 0.085, 0.08,0.075, 0.07, or 0.065. Furthermore, in certain embodiments, themesoporous zeolite can have a dV/D in the range of 0.002 to 0.1, 0.0035to 0.95, 0.0035 to 0.09, 0.004 to 0.08, 0.0045 to 0.08, 0.0075 to 0.075,0.01 to 0.07, 0.015 to 0.07, 0.02 to 0.065, or 0.025 to 0.65.

Furthermore, in certain embodiments, the mesoporous zeolite candemonstrate an inflection in an Ar adsorption isotherm at 87 K between aP/P0 at 0.1 to 0.99.

Additionally, in various embodiments, the mesoporous zeolite can have amesopore ratio that is greater than the initial zeolite, low SARzeolite, and/or acid-treated zeolite. For example, the mesoporouszeolite can have a mesopore ratio that is at least 5, 10, 25, 50, 100,or 200 percent greater than the mesopore ratio of the initial zeolite,low SAR zeolite, and/or acid-treated zeolite. Moreover, in certainembodiments, the mesoporous zeolite can have a mesopore ratio that is atleast 0.05, 0.1, 0.15, 0.2, or 0.25 greater than the mesopore ratio ofthe initial zeolite, low SAR zeolite, and/or acid-treated zeolite.

In other embodiments, the mesoporous zeolite can have a mesopore ratioof at least 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7 and/or not more than 1.2, 1,0.95, or 0.9. Moreover, in certain embodiments, the mesoporous zeolitecan have a mesopore ratio in the range of 0.2 to 1.2, 0.3 to 1, 0.3 to1, 0.4 to 0.95, 0.5 to 0.9, 0.6 to 0.9, or 0.7 to 0.9.

Furthermore, in various embodiments, the mesoporous zeolite has a lowernPA-TPD relative to the initial zeolite. For example, the mesoporouszeolite can have an nPA-TPD that is at least 10, 20, 30, or 40 percentand/or not more than 200, 100, 90, or 75 percent lower than the initialzeolite. Furthermore, in certain embodiments, the mesoporous zeolite canhave an nPA-TPD that is 10 to 200 percent, 20 to 100 percent, 30 to 90percent, or 40 to 75 percent lower than the initial zeolite.

In various embodiments, the mesoporous zeolite has a lower ZSA relativeto the acid-treated zeolite. For example, the mesoporous can have a ZSAthat is at least 10, 25, 50, 100, or 150 percent and/or not more than500, 400, 300, 250, or 200 percent lower than the ZSA of theacid-treated zeolite.

In other embodiments, the mesoporous zeolite has a MSA and BET surfacearea that is greater than the acid-treated zeolite. For example, themesoporous zeolite can have a BET that is at least 10, 20, 30, 40, or 50percent and/or not more than 200, 150, 125, 100, or 95 percent greaterthan the BET of the acid-treated zeolite. Furthermore, in certainembodiments, the mesoporous zeolite can have a MSA that is at least 10,30, 50, 100, or 200 percent and/or not more than 1,000, 750, 500, 400,or 300 percent greater than the MSA of the acid-treated zeolite.

In certain embodiments, the mesoporous zeolite can have a lower UCSrelative to the initial zeolite. For example, the mesoporous zeolite canhave a UCS that is at least 0.01, 0.02, 0.04, 0.06, 0.08, or 0.10 lessthan the UCS of the initial zeolite.

The preferred forms of the invention described above are to be used asillustration only, and should not be used in a limiting sense tointerpret the scope of the present invention. Modifications to theexemplary embodiments, set forth above, could be readily made by thoseskilled in the art without departing from the spirit of the presentinvention.

This invention can be further illustrated by the following examples ofembodiments thereof, although it will be understood that these examplesare included merely for the purposes of illustration and are notintended to limit the scope of the invention unless otherwisespecifically indicated.

EXAMPLES Examples 1-3

Samples of ZSM-5 (CBV2314 from Zeolyst International), mordenite (CV10Afrom Zeolyst International), and NaY zeolite (provided by W. R. Grace)were subjected to desilication pretreatments under varying reactionconditions. Various properties of these zeolites are depicted in Table1, below.

In the first study, 227 g of ZSM-5 (CBV2314) was heated with 128 g of50% NaOH in 800 g of deoionized water at 80° C. for 1 hour. Theresulting mixture was filtered and washed to yield a desilicated zeolitelabeled as “DS-1” in Table 1, which had a crystallinity of 67% (relativeto the initial ZSM-5).

Next, 22.7 g of ZSM-5 (CBV2314) was heated with 19.2 g of 50% NaOH in 80g of deoionized water at 80° C. for 1 hour. The resulting mixture wasfiltered and washed to yield a desilicated zeolite labeled as “DS-2” inTable 1, which had a crystallinity of 37% (relative to the initialZSM-5).

In the second study, 58 g of mordenite (CBV10A) was heated with 24 g of50% NaOH in 128 g of deoionized water at 80° C. for 1 hour. Theresulting mixture was filtered and washed to yield a desilicated zeolitelabeled as “DS-1” in Table 1, which had a crystallinity of 86% (relativeto the initial mordenite).

Next, 58 g of mordenite (CBV10A) was heated with 24 g of 50% NaOH in 128g of deoionized water at 80° C. for 24 hours. The resulting mixture wasfiltered and washed to yield a desilicated zeolite labeled as “DS-2” inTable 1, which had a crystallinity of 63% (relative to the initialmordenite).

In the third study, 205 g of NaY zeolite was heated with 72 g of 50%NaOH in 600 g of deoionized water at 80° C. for 1 hour. The resultingmixture was filtered and washed to yield a desilicated zeolite labeledas “DS-1” in Table 1, which had a crystallinity of 97% (relative to theinitial NaY zeolite).

Next, 205 g of NaY zeolite was heated with 144 g of 50% NaOH in 600 g ofdeoionized water at 80° C. for 1 hour. The resulting mixture wasfiltered and washed to yield a desilicated zeolite labeled as “DS-2” inTable 1, which had a crystallinity of 93% (relative to the initial NaYzeolite).

Table 1, below, depicts the properties of the desilicated zeolitescompared to the starting initial zeolites. It should be noted that “PV”in Table 1 signifies “pore volume” and that “Meso Ratio” represents theabove-described mesopore ratio. Argon sorption was used to characterizethe porosity of the zeolites. The starting initial zeolites were used asthe crystallinity standard. BET surface area was calculated from the Arsorption results. ZSA and MSA were calculated using t-plot method alsofrom the Ar sorption results. All pore volumes (0-20 Å, 20-80 Å, and20-300 Å, all in cc/g) were calculated using the NLDFT module in theQuadraWin program provided by Quantachrome Instruments from the Arsorption results.

TABLE 1 0-20 20-80 20-300 UCS Å Å Å Meso dV/ ZSA MSA BET Sample XRD %(Å) SAR cc/g cc/g cc/g Ratio log(D) m²/g m²/g m²/g ZSM-5 100 N/A 24.10.20 0.01 0.02 0.55 0.04 389 39 428 DS-1 67 N/A 14.6 0.12 0.05 0.15 0.350.32 204 107 311 DS-2 37 N/A 9.7 0.09 0.07 0.15 0.45 0.24 126 141 267Mordenite 100 N/A 13.2 0.16 0.01 0.02 0.63 0.03 302 32 334 DS-1 86 N/A11.2 0.11 0.05 0.08 0.56 0.16 184 135 319 DS-2 63 N/A 8.1 0.09 0.03 0.080.41 0.15 149 82 231 NaY 100 24.65 5.6 0.36 0.01 0.02 0.39 0.05 832 25857 DS-1 97 24.68 4.9 0.31 0.00 0.02 0.21 0.17 731 26 757 DS-2 93 24.744.1 0.30 0.00 0.02 0.22 0.23 734 29 763

As shown in Table 1, the desilication pretreatments introduced somemesoporosity in the zeolites.

Example 4

In this study, ZSM-5 (CBV2314 from Zeolyst International) was treatedwith 8 mmol/g NaOH solution at 80° C. for 1 hour, as described inExample 1, which was then filtered and washed. The resulting productstill had a ZSM-5 structure as confirmed by XRD, but the SAR was reducedto about 15. Also, it was observed that some mesoporosity was introducedduring the desilication step. The product was then treated in sulfuricacid (2M, 12 cc/g zeolite) to dealuminate the zeolite to a SAR of about37. The dealuminated zeolite was then treated with CTAC (0.5 g/gzeolite) and NaOH (0.5 mmol/g zeolite) at ˜20% solid content. Theproduct (“Rived”) was then ammonium exchanged and calcined to removesurfactant templates.

FIG. 1 depicts the Ar sorption isotherms of the starting ZSM-5,NaOH-desilicated zeolite, H₂SO₄-dealuminated zeolite, and the mesoporousfinal product. The corresponding properties of the zeolites are listedin Table 2. FIG. 2 depicts the NLDFT pore size distributions of thetreated zeolites. It should be noted that the mesopore ratio (“MesoRatio”), as depicted in Table 2, was measured after subjecting thezeolite to ammonium exchange. It should also be noted that the rivedsample (i.e., mesoporous sample) contained an inflection in an Aradsorption isotherm at 87 K between a P/P0 at 0.1 to 0.99.

As shown in Table 2, argon sorption was used to characterize theporosity of the zeolites. The starting initial zeolites were used as thecrystallinity standard. All pore volumes (0-20 Å, 20-80 Å, and 20-300 Å,all in cc/g) were calculated using the NLDFT module in the QuadraWinprogram provided by Quantachrome Instruments from the Ar sorptionresults.

TABLE 2 0-20 Å 20-80 Å 20-300 Å nPA- Meso dV/ Sample XRD % SAR cc/g cc/gcc/g TPD Ratio log(D) CBV2314 100 24.1 0.20 0.01 0.02 1.20 0.55 0.04NaOH Desilicated 60 14.6 0.16 0.08 0.11 1.27 0.67 0.19 H₂SO₄Dealuminated61 37.1 0.16 0.08 0.14 N/A 0.56 0.22 Rived (calcined) 60 36.1 0.14 0.150.23 0.79 0.65 0.91

Example 5

In this study, 1136.4 g of ZSM-5 (CBV2314 from Zeolyst International)was treated in 720 g of 50% NaOH solution (hydroxide dose at 9 mmol/glevel) and 4,000 g of water at 80° C. for 4 hours, which yielded adesilicated ZSM-5 that had a SAR of 13.5 and relative crystallinity of54%. Following H₂SO₄ treatment at 80° C. for 3 hours at 3 differentseverities (0.3, 0.45, and 0.6 M concentrations), the acid-dealuminatedzeolites had 3 SAR values at ˜24, 32, and 35, respectively (see Table 3,below). Treatment of the dealuminated zeolites (labeled “A1,” “A2,” and“A3” in Table 2) with CTAC (0.5 g/g) in NaOH solution (0.75 mmol/g) at80° C. for 1 hour yielded three mesostructured zeolites (i.e., “rived”zeolites), the properties of which are listed in Table 3.

Argon sorption was used to characterize the porosity of the zeolites inTable 3. It should be noted that Rived Samples 1, 2, and 3, as shown inTable 3, all contained inflections in their Ar adsorption isotherms at87 K between a P/P0 at 0.1 to 0.99. The starting initial zeolites wereused as the crystallinity standard. BET surface area was calculated fromthe Ar sorption results. ZSA and MSA were calculated using t-plot methodalso from the Ar sorption results. All pore volumes (0-20 Å, 20-80 Å,and 20-300 Å, all in cc/g) were calculated using the NLDFT module in theQuadraWin program provided by Quantachrome Instruments from the Arsorption results.

TABLE 3 0-20 Å 20-80 Å 20-300 Å Meso dV/ ZSA MSA BET Sample XRD % SARcc/g cc/g cc/g Ratio log(D) m²/g m²/g m²/g Desilicated 54 13.5 0.09 0.040.13 0.34 0.25 137 93 229 CBV2314 A1 (0.3M) 55 24.3 0.17 0.07 0.17 0.380.37 277 165 442 Rived-1 67 24.1 0.15 0.21 0.23 0.90 1.42 168 320 487 A2(0.45M) 52 32.9 0.17 0.07 0.16 0.42 0.24 284 162 445 Rived-2 67 31.70.14 0.22 0.29 0.75 2.31 136 343 478 A3 (0.6M) 51 35.1 0.16 0.06 0.170.38 0.27 263 159 422 Rived-3 67 35.2 0.13 0.26 0.31 0.84 2.99 97 384481

Example 6

In this study, the mesoporosity introduced by desilication with orwithout surfactant to the initial zeolite (instead of the correspondinglow SAR zeolite) was compared. In one experiment, ZSM-5 (CV3024E fromZeolyst International) was treated with a NaOH solution (13% solid, 4.5mmol/g NaOH at 80° C. for 4 hours) to yield a desilicated zeolite. Inanother experiment, surfactant (CTAC at 0.3 g/g zeolite) was also addedwhile all other conditions were the same as the first experiment. Asshown in FIG. 3, the mesopore size distribution of the two zeolites wasvery similar. It was concluded that under the reaction conditions,desilication was the dominating process at introducing mesoporosity evenwith the use of CTAC. FIG. 4 depicts the corresponding NLFDT pore sizedistributions calculated from the adsorption isotherms of the treatedzeolites.

Example 7

In this study, 1,060 g of mordenite (CBV10A from Zeolyst International)was slurried in 2,411 g of deionized water and heated to 80° C.Afterwards, 215 g of 50% NaOH was then added to the slurry and themixture was stirred at 80° C. for 24 hours. After filtration andwashing, the desilicated mordenite was dried overnight at 80° C.Subsequently, 18 g of the desilicated mordenite was then added into 180mL of 0.35 M H₂SO₄ at 80° C. and stirred for 3 hours. After filtrationand washing, 14 g of the acid-treated mordenite was then added into 72 gwater. Then 20 g of 30% CTAC was added and the pH of the slurry wasadjusted to 7.0, after which 48 g 50% NaOH was then added to the slurryand the mixture was stirred for 2 hours at 80° C. before filtration andwashing. Finally, Na₂O and surfactant removal was then accomplished byfour solvent extractions by isopropanol azeotrope at refluxingtemperature. As shown in Table 4 and FIGS. 5 and 6, the resultingproduct was a mesostructured mordenite. FIG. 5 depicts the Ar sorptionisotherm of the mesostructured product, while FIG. 6 depicts the NLDFpore size distribution calculated from the adsorption isotherms.

As shown in Table 4, argon sorption was used to characterize theporosity of the zeolites. The starting initial zeolite was used as thecrystallinity standard. BET surface area was calculated from the Arsorption results. ZSA and MSA were calculated using t-plot method alsofrom the Ar sorption results. All pore volumes (0-20 Å, 20-80 Å, and20-300 Å, all in cc/g) were calculated using the NLDFT module in theQuadraWin program provided by Quantachrome Instruments from the Arsorption results.

TABLE 4 0-20 Å 20-80 Å 20-300 Å Meso dV/ ZSA MSA BET Sample XRD % SARcc/g cc/g cc/g Ratio log(D) m²/g m²/g m²/g CBV10A 100  13.2 0.16 0.010.02 0.63 0.03 302  32 334 Desilicated CBV10A 90 11.4 N/A N/A N/A N/AN/A N/A N/A N/A Dealuminated N/A 17.4 N/A N/A N/A N/A N/A N/A N/A N/AMesostructured 98 17.1 0.18 0.08 0.12 0.69 0.81 319 149 468

Example 8

In this study, it was shown that the desilication pretreatment couldalso be applied to Y zeolite. Specifically, a slurry with 25% solids ofNaY zeolite (provided by W. R. Grace) was added to a 50% NaOH solutionat 6 mmol NaOH/g zeolite at 80° C. The reaction was stirred at 80° C.for 18 hours before it was filtered and washed thoroughly. Then 46 g ofthe desilicated NaY zeolite (“NaY-D”) was mixed with 83 g water andmagnetically stirred and heated to 80° C. After adjusting the pH of theslurry to ˜7 using 3M HNO₃, 44.4 g of 23% citric acid was pumped in over1 hour. The reaction mixture was stirred for another 2 hours at 80° C.before it was filtered and washed. The acid-treated zeolite cake(“NaY-DA”) was mixed with water and 30% CTAC solution at (0.1 g CTAC/gzeolite level). The mixture was stirred and heated to 80° C. The pH ofthe slurry was then adjusted to 7 using 50% NaOH, followed by additionof another dose of 50% NaOH at 0.38 mmol NaOH/g zeolite level. Thereaction mixture was stirred at 80° C. for an hour before it wasfiltered and washed thoroughly. After reducing the % Na₂O to ˜2.5% byion exchange with NH₄NO₃ solution, the dried zeolite was thenultrastabilized at 550° C. and 100% steam for 2 hours, followed bycalcinations in flowing air for another 2 hours. After further reducingthe % Na₂O by another ion exchange with NH₄NO₃ solution, the final USYproduct was obtained (“USY-R”), which has the same SAR (aluminumcontent) as the starting NaY zeolite.

The main properties of the zeolites depicted above are shown in Table 5.Conceivably, by varying the severity of the desilication pre-treatmentand the severity of the dealumination, mesoporous zeolite Y withdifferent chemical compositions (SAR) and micro/meso porositycombinations can be obtained. Argon sorption was used to characterizethe porosity of the zeolites. The starting initial zeolite was used asthe crystallinity standard. BET surface area was calculated from the Arsorption results. ZSA and MSA were calculated using t-plot method alsofrom the Ar sorption results. All pore volumes (0-20 Å, 20-80 Å, and20-300 Å, all in cc/g) were calculated using the NLDFT module in theQuadraWin program provided by Quantachrome Instruments from the Arsorption results.

TABLE 5 0-20 Å 20-80 Å 20-300 Å Meso dV/ ZSA MSA BET Sample % XRD SARUCS cc/g cc/g cc/g Ratio log(D) m²/g m²/g m²/g NaY 100 5.6 24.65 0.360.01 0.02 0.46 0.05 832 25 857 NaY-D 94 4.1 24.73 0.37 0.01 0.02 0.290.13 890 46 936 NaY-DA 78 5.8 24.68 0.36 0.02 0.05 0.48 0.22 870 87 957USY-R 85 5.6 24.54 0.28 0.08 0.12 0.65 0.23 645 157 801

Example 9

This example demonstrated that the sizes of the mesopores introducedduring the surfactant treatment step corresponded to the size of thesurfactants. A starting desilicated CBV2314 (from Zeolyst International)was subjected to an acid treatment (0.4 M H₂SO₄, 12 cc/g zeolite, 80° C.for 3 hours) and then the resulting mixture was filtered and washedthree times with hot deionized water. The acid-treated zeolite was thendivided into two portions and added to a CTAC (cetyltrimthylammoniumchloride) solution in water (0.5 g CTAC/g zeolite) for one reaction andto a BTAC (behenyltrimethylammonium chloride) solution in water (0.5 gBTAC/g zeolite) in the other reaction. Both mixtures were heated to 80°C. After adjusting the pH of the mixtures to 7 using a 50% NaOHsolution, additional 50% NaOH solution (0.75 mmol NaOH/g zeolite) wasadded and the mixtures were heated with stirring for 1 hour. Thereaction mixtures were then filtered and washed three times with hotdeionized water. After being dried at 80° C. overnight, the zeoliteswere then treated with a NH₄NO₃ solution to reduce the Na₂O % to below0.2% (as measured by XRF). The zeolites were then dried again andcalcined under flowing nitrogen at 550° C. for 2 hours and flowing airat 550° C. for another 2 hours to remove the surfactants.

Argon sorption was used to characterize the porosity of the zeolites.The starting initial zeolites were used as the crystallinity standard.BET surface area was calculated from the Ar sorption results. ZSA andMSA were calculated using t-plot method and the Ar sorption results. Allpore volumes (0-20 Å, 20-80 Å, and 20-300 Å, all in cc/g) werecalculated using the NLDFT module in the QuadraWin program provided byQuantachrome Instruments from the Ar sorption results.

FIG. 7 depicts the Ar sorption isotherm at 87 K of the CTAC-treated andBTAC-treated zeolites, while FIG. 8 depicts the NLDFT pore sizedistributions calculated from the adsorption isotherms. As shown in FIG.8, the NLDFT pore size distribution suggested that the sizes of themesopores in the two zeolites corresponded to the sizes of thesurfactants used in the reactions: CATC-treated (˜4.5 nm) andBTAC-treated (˜5.5 nm).

Table 6, below, depicts the properties of the desilicated startingzeolite, the acid-treated zeolite, the CTAC-treated zeolite, and theBTAC-treated zeolite.

TABLE 6 0-20 Å 20-80 Å 20-300 Å ZSA MSA BET Sample Names % XRD SAR cc/gcc/g cc/g m²/g m²/g m²/g Meso Ratio dV/log(D) Desilicated 63 15.1 0.080.04 0.12 131 77 208 0.29 0.18 Acid-treated 60 29.6 0.17 0.04 0.13 287129 415 0.31 0.21 CTAC-Treated 67 27.8 0.14 0.23 0.30 180 285 475 0.771.40 BTAC-Treated 65 27.8 0.15 0.25 0.39 197 291 488 0.65 1.45

Example 10

This example demonstrates the effects of realumination together withdesilication to reduce the silica to alumina molar ratio of an initialzeolite. In this example, 28.4 g of CBV2314 (Zeolyst International) wasadded to 100 g of deionized water. After being heated to 80° C., the pHof the slurry was adjusted to 7 and a mixture of 17.4 g of 50% NaOH and0.61 g NaAlO₂ was added to the reaction with stirring. After 4 hours,the reaction was filtered and washed with hot deionized water. In twoseparate experiments, the same amounts of CBV2314 and deionized waterwere used and the same procedure was followed except that 16.85 g 50%NaOH and 1.23 g NaAlO₂ was used in the second reaction and 16.2 g 50%NaOH and 1.84 g NaAlO₂ was used in the third reaction. In bothexperiments, the total hydroxide doses were maintained at 9 mmol/g. Theresults in Table 7 suggest that realumination together with desilicationworked to further reduce the silica to alumina molar ratio compared todesilication only as described in Example 5. Furthermore, the powderX-ray diffraction patterns shown in FIG. 9 demonstrate that all zeolitesmaintained the ZSM-5 structure. It should be noted that the sharp peakat ˜28, 47, and 56 2-Theta in FIG. 9 are from Si internal standard addedto the samples.

TABLE 7 20- 0-20 20-80 300 XRD Å Å Å ZSA MSA BET Sample % SAR cc/g c/gcc/g m²/g m²/g m²/g Desilicated 54 13.5 0.09 0.04 0.13 137 93 229CBV2314 Realuminated 1 49 11.2 0.11 0.06 0.10 172 109 281 Realuminated 248 9.9 0.11 0.06 0.16 170 132 302 Realuminated 3 40 8.9 0.09 0.05 0.14140 107 247

Example 11

This example demonstrates that a sequential desilication step followedby a realumination step can effectively lower the SAR of a startingzeolite (CBV2314 with a SAR of ˜24). In this study, 285.1 g (250 g ondry basis) of CBV2314 was added into 900 g of DI water at 65° C. withstirring. After adjusting the pH of the slurry to ˜7.0, 130 g of 50%NaOH was added. After 30 minutes at 65° C., the reaction mixture wasvacuum filtered and washed 20 times with hot DI water. The resultingdesilicated ZSM-5 product had a SAR of 16.8.

Subsequently, 135.1 g of the desilicated ZSM-5 (62.4 g on a dry basis)was then added to 177 g of DI water at 65° C. with stirring. Afterwards,6.14 g of NaAlO₂ (99%) was then added. After 3 hours at 65° C., thereaction mixture was vacuum filtered and washed 20 times with hot DIwater. The solid was then dried at room temperature to obtain arealuminated ZSM-5 having a SAR of 10.8.

Afterwards, 38 g (20 g on a dry basis) of the realuminated ZSM-5 wasthen added into 55.3 g of DI water at 80° C. with stirring.Subsequently, 22.4 g of 70% H₂SO₄ was then added. After 1 hour at 80°C., the reaction mixture was vacuum filtered and washed 3 times with hotDI water. The SAR of the dealuminated ZSM-5 was then raised to 37.4.

Next, 25.4 g (11.5 g on a dry basis) of the dealuminated ZSM-5 obtainedas described above was added to 37.1 g of DI water 80° C. with stirring.Afterwards, 19.2 g of 30% CTAC was then added. After adjusting the pH to˜7, 1.38 g of 50% NaOH was added. After 1 hour at 80° C., the reactionmixture was vacuum filtered and washed 3 times with hot DI water. Theresulting material was then calcined in static air to remove thesurfactant (1° C./min from room temperature to 600° C. and then held at600° C. for 2 hours before cooling to room temperature). The texturalproperties of the ZSM-5 zeolites during the study are listed below inTable 8. The inflection at P/Po around 0.4-0.7 in the adsorptionisotherm is clearly observable in FIG. 10, which demonstrates thesurfactant-templated mesoporosity.

TABLE 8 0-20 Å 20-80 Å 20-300 Å ZSA MSA BET Sample XRD % SAR cc/g c/gcc/g m²/g m²/g m²/g CBV2314 100  24.1 0.20 0.01 0.02 393  37 430Desilicated ZSM-5 74 16.8 0.14 0.06 0.17 224 136 359 Realuminated ZSM-565 10.8 0.12 0.07 0.16 187 133 320 Dealuminated ZSM-5 N/A 37.4 N/A N/AN/A N/A N/A N/A Rived ZSM-5 80 33.7 0.13 0.20 0.30 139 303 442

Example 12

This example demonstrates that desilication and realumination can alsobe carried out in a single step treatment with both NaOH and NaAlO₂. Inthis example, 1146.8 g (1,000 g on a dry basis) of CBV2314 was added to2,639.0 g of DI water at 65° C. with stirring. Afterwards, 109.8 g of99% NaAlO₂ and 428.8 g of 50% NaOH were mixed and added to the reactionmixture. After 3 hours at 65° C., the reaction mixture was vacuumfiltered, washed 20 times with hot Di water, and dried at roomtemperature overnight. The SAR of the resulting DeSil-ReAl ZSM-5 wasreduced to 9.4.

Subsequently, 1,900 g of the DeSil-ReAl ZSM-5 (787 g on a dry basis) wasadded to 1,867.8 g of DI water at 80° C. with stirring. Next, 550.7 g of70% H₂SO₄ was then added. After 1 hour at 80° C., the mixture wasfiltered, washed, and dried at room temperature overnight. The SAR ofthe dealuminated ZSM-5 was raised to 27.9.

Next, 1,040 g (529 on a dry basis) of the dealuminated ZSM-5 was thenadded to 1,855.6 g of DI water at 80° C. with stirring. Subsequently,882.3 g of 30% CTAC was then added and the pH of the slurry was adjustedto 7. Afterwards, 31.8 g of 50% NaOH was then added. After 1 hour at 80°C., the reaction mixture was filtered, washed with hot DI water, andthen dried at 80° C. overnight. The rived ZSM-5 was then calcined instatic air to remove surfactant (1° C./min from room temperature to 550°C. and then held at 550° C. for 2 hours before cooling to roomtemperature). Textural properties of the zeolites are listed below inTable 9. The inflection at P/Po around 0.4-0.7 in the adsorptionisotherm as shown in FIG. 11 is very clear, which demonstrates thesurfactant-templated mesoporosity.

TABLE 9 0-20 Å 20-80 Å 20-300 Å ZSA MSA BET Sample XRD % SAR cc/g c/gcc/g m²/g m²/g m²/g CBV2314 100 24.1 0.20 0.01 0.02 393 37 430DeSil-ReAl ZSM-5 51 9.4 0.11 0.06 0.13 157 130 287 Dealuminated ZSM-5 6527.9 0.16 0.09 0.17 225 213 438 Rived ZSM-5 73 27.4 0.13 0.20 0.25 127315 442

DEFINITIONS

It should be understood that the following is not intended to be anexclusive list of defined terms. Other definitions may be provided inthe foregoing description, such as, for example, when accompanying theuse of a defined term in context.

As used herein, the terms “a,” “an,” and “the” mean one or more.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination, B and C in combination; orA, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the terms “having,” “has,” and “have” have the sameopen-ended meaning as “comprising,” “comprises,” and “comprise” providedabove.

As used herein, the terms “including,” “include,” and “included” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

What is claimed is:
 1. A method of forming a mesoporous zeolitecomprising: (a) modifying an initial zeolite to thereby yield a low SARzeolite, wherein said low SAR zeolite has a silica to alumina molarratio that is at least 20 percent lower than said initial zeolite,wherein said silica to alumina molar ratio of said low SAR zeolite ishigher than the destabilizing SAR value of said initial zeolite; (b)treating said low SAR zeolite with an acid to thereby yield anacid-treated zeolite; (c) contacting at least a portion of saidacid-treated zeolite with a pore forming agent to thereby form saidmesoporous zeolite.
 2. The method of claim 1, wherein said modifying ofstep (a) comprises desilicating or aluminating said initial zeolite. 3.The method of claim 2, wherein said desilicating comprises contactingsaid initial zeolite with a base.
 4. The method of claim 3, wherein thebase can be selected from the group consisting of ammonium hydroxide,tetraalkyl ammonium hydroxides, sodium hydroxide, potassium hydroxide,sodium carbonate, potassium carbonate, amines, and mixtures of two ormore thereof.
 5. The method of claim 2, wherein said desilicating occursat a temperature in the range of 20 to 160° C. and over a time period of0.5 to 48 hours.
 6. The method of claim 1, wherein said mesoporouszeolite has a dV/log(d) in the range of 0.3 to
 100. 7. The method ofclaim 1, wherein said low SAR zeolite has a mesopore ratio that is lowerthan the mesopore ratio of said initial zeolite.
 8. The method of claim1, wherein said low SAR zeolite has a mesopore ratio that is at least 25percent lower than the mesopore ratio of said initial zeolite.
 9. Themethod of claim 1, wherein said pore forming agent comprises asurfactant.
 10. The method of claim 1, wherein said initial zeolitecomprises a ZSM-5, a mordenite, a faujasite, a BEA zeolite, a LTLzeolite, an FRE zeolite, or combinations thereof.
 11. A method offorming a mesoporous zeolite comprising: (a) providing a low SARzeolite, wherein said low SAR zeolite is selected from the groupconsisting of a ZSM-5 having a silica to alumina molar ratio of 17 orless, a mordenite having a silica to alumina molar ratio of 10 or less,a faujasite having a silica to alumina molar ratio of 5 or less, a BEAzeolite having a silica to alumina molar ratio of 15 or less, a LTLzeolite having a silica to alumina molar ratio of 5 or less, an FREzeolite having a silica to alumina molar ratio of 10 or less, andmixtures thereof, wherein said providing comprises desilicating aninitial zeolite, wherein said desilicating comprises contacting saidinitial zeolite with a base at a temperature in the range of 20 to 160°C. and over a time period of 0.5 to 48 hours; (b) treating said low SARzeolite with an acid to thereby yield an acid-treated zeolite; and (c)contacting at least a portion of said acid-treated zeolite with a poreforming agent to thereby form said mesoporous zeolite.
 12. The method ofclaim 11, wherein the base can be selected from the group consisting ofammonium hydroxide, tetraalkyl ammonium hydroxides, sodium hydroxide,potassium hydroxide, sodium carbonate, potassium carbonate, amines, andmixtures of two or more thereof.
 13. The method of claim 11, whereinsaid mesoporous zeolite has a dV/log(d) in the range of 0.3 to
 100. 14.The method of claim 11, wherein said mesoporous zeolite has a mesoporeratio that is at least 25 percent greater than the mesopore ratio ofsaid low SAR zeolite.
 15. The method of claim 11, wherein said poreforming agent comprises a surfactant.
 16. A method of forming amesoporous zeolite comprising: (a) subjecting an initial zeolite to aframework modification process to thereby produce a framework-modifiedzeolite, wherein said framework-modified zeolite has a silica to aluminamolar ratio that is lower than said initial zeolite, wherein saidframework modification process comprises desilicating said initialzeolite at a temperature in the range of 20 to 160° C. and over a timeperiod of 0.5 to 48 hours to thereby form said framework-modifiedzeolite, wherein said desilicating comprises contacting said initialzeolite with a base; (b) contacting at least a portion of saidframework-modified zeolite with an acid to thereby form an acid-treatedzeolite; and (c) contacting at least a portion of said acid-treatedzeolite with a pore forming agent to thereby form said mesoporouszeolite.
 17. The method of claim 16, wherein the base can be selectedfrom the group consisting of ammonium hydroxide, tetraalkyl ammoniumhydroxides, sodium hydroxide, potassium hydroxide, sodium carbonate,potassium carbonate, amines, and mixtures of two or more thereof. 18.The method of claim 16, wherein said mesoporous zeolite has a peakdV/log(d) in the range of 0.3 to
 100. 19. The method of claim 16,wherein said framework-modified zeolite has a mesopore ratio that is atleast 25 percent lower than the mesopore ratio of said initial zeolite.20. The method of claim 16, wherein said acid comprises hydrochloricacid, sulfuric acid, nitric acid, acetic acid, sulfonic acid, oxalicacid, citric acid, ethylenediaminetetraacetic acid (“EDTA”), tartaricacid, malic acid, glutaric acid, succinic acid, and mixtures of two ormore thereof.
 21. The method of claim 16, wherein said mesoporouszeolite has a mesopore ratio that is at least 25 percent greater thanthe mesopore ratio of said low SAR zeolite.
 22. The method of claim 16,wherein said pore forming agent comprises a surfactant.